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PDM Installation & Configuration: Batteries

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00:00 - Almost universally, the automotive project you're working on is going to involve a battery.
00:05 In this course section, we'll discuss the reasons we use a battery in our automotive electrical setup, look at the different types of batteries you're likely to encounter and makes sure we know how to isolate them in a safe and racing class rules compliant way.
00:17 To begin with, why do we need the battery? Well the most obvious reason is to supply electrical energy to the starter motor to get the internal combustion engine up and running.
00:27 But the battery also serves another very important purpose.
00:30 And that is smoothing out the electrical voltage supply level.
00:34 As our vehicle runs and drives, lots of electrical loads are being switched on and off all the time and the stopping and starting of current flow through these devices can cause the voltage level in the car to jump up and down erratically.
00:47 The alternator will be monitoring this voltage level and increasing or decreasing its output current to try and keep the system voltage stable.
00:55 But this feedback system isn't instant and even short lived voltage spikes can damage our electrical components.
01:02 The battery in the system is a reservoir of electrical energy.
01:06 When an electrical load in the car is switched on, the battery can supply the newly required current instantly while the alternator is taking time to increase its output current to meet the new system demand.
01:18 At which point it takes over, supplying that new electrical load as well as recharging what was just used from the battery.
01:26 The reverse of this is also true.
01:28 When the alternator is supplying current to an electrical load and this load is then switched off, there's a period of time when the alternator is reacting to this change where it will be supplying too much current.
01:39 This extra current gets dumped into the battery which avoids a voltage spike in our system.
01:45 This can be a slightly tricky concept to visualise but there's a common and pretty good analogy that helps to get a picture of what's going on.
01:51 If we think of the battery as a large water storage tank, the bottom of which we have a tap attached to that we can open to supply water as well as a pump attached that will refill that tank with water from another source like a nearby river or lake.
02:07 In this analogy, the flow of water is the current and the height of the water in the tank is the system voltage level.
02:14 The pump is the alternator and the tap is the connected electrical loads.
02:19 We can draw a little water out of the tank from our tap or we can pump a little water back into it and its overall water level won't change much.
02:28 As both our supply tap and our pump are attached to the bottom of the tank, the pressure or voltage that these points see is completely determined by the water level in that tank.
02:40 This level doesn't change much so our system pressure remains pretty constant.
02:45 With a good idea of why we have a battery in our system, let's have a look at the different types of batteries you're likely to encounter in the performance automotive realm.
02:52 These are going to be lead acid, absorbed glass mat, often called AGM and lithium chemistry.
02:58 Traditionally the most common type of battery you're likely to encounter is a lead acid battery.
03:04 This is a conventional automotive battery that uses lead plates suspended in an acidic electrolyte which causes a chemical reaction that generates our electrical energy.
03:13 These batteries have a couple of downsides.
03:16 As lead is a very dense materials, these batteries are heavy.
03:19 The electrolyte in them is a fluid meaning that they need to be kept upright to avoid spilling which limits the mounting orientations available.
03:26 Now they do have an upside as well though in that is cost and they are quite cheap.
03:31 Absorbed glass mat or AGM batteries still use lead and the same chemistry in their construction but they have impregnated fibreglass mats in place of that liquid electrolyte.
03:41 This means they're still relatively heavy but they have no liquid to spill so they can be mounted in any orientation.
03:46 Lithium chemistry batteries are becoming more and more common in the performance automotive world, much of their development being driven by the motorcycle racing world where packaging and mounting is completely critical.
03:57 Lithium chemistry batteries for internal combustion automotive use are of the lithium iron phosphate type as opposed to the lithium ion type more commonly associated with EV applications.
04:10 These batteries are significantly lighter than a similar capacity lead based battery, physically smaller and can be mounted in any orientation.
04:19 They are expensive however and will require some research to ensure they're correct for your application.
04:24 At the very least, ensure any lithium chemistry battery you're using in your project has an integrated battery management system to make sure the battery is protected from a dead short, it's properly charged by the alternator, those individual cells in there will remain balanced and it won't be damaged by over discharging.
04:41 There is a hybrid approach to this used on severely space or weight constrained applications.
04:46 That is to have a small capacity, typically lithium chemistry battery mounted on the vehicle to power the electronics while the engine is not running and smooth that supply from the alternator when it is.
04:58 This battery is not capable of supplying the large current required by the starter motor though.
05:03 So this is instead supplied from an external battery via a power connector.
05:07 The power connector could be of any type that can handle the large starter motor current.
05:11 The most commonly used is a type known as an Anderson connector.
05:15 These connectors are a great design because each half is actually exactly the same part and one is just flipped upside down when they're plugged into each other.
05:23 They also have positive and negative sides embossed into their plastic bodies meaning it's much harder to accidentally make a reverse polarity connection.
05:31 These connectors most commonly come in 3 different colours of plastic body, grey, black and red.
05:37 The grey and black bodied connectors will intermate with one another but the red ones are keyed differently so will only mate to another red connector body.
05:45 These connectors also come in various sizes but I would suggest going with the SB120 size.
05:50 This connector body is rated to 120 amps of continuous current but will hand a higher starter motor current over the short time that the engine is being cranked.
06:01 In this module we've looked at the reasons we need a battery in our automotive electrical system, being primarily for starting the engine and smoothing the output of the alternator to avoid damaging the electronics in the vehicle.
06:12 We've discussed the pros and cons of 3 common types of battery that you're likely to encounter in the performance automotive world and looked at a hybrid solution enabling the use of a small capacity onboard battery with a larger capacity external battery that's only used when we're starting the engine in the pits.

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